RRDFETCH(1)                          rrdtool                         RRDFETCH(1)

NAME
     rrdfetch - Fetch data from an RRD.

SYNOPSIS
     rrdtool  fetch  filename CF [--resolution|-r resolution] [--start|-s start]
     [--end|-e end] [--align-start|-a] [--daemon|-d address]

DESCRIPTION
     The fetch function is normally used internally by the graph function to get
     data from RRDs. fetch will analyze the RRD and try to retrieve the data  in
     the resolution requested.  The data fetched is printed to stdout. *UNKNOWN*
     data is often represented by the string "NaN" depending on your OS's printf
     function.

     filenamethe name of the RRD you want to fetch the data from.

     CF      the  consolidation function that is applied to the data you want to
             fetch (AVERAGE,MIN,MAX,LAST)

     --resolution|-r resolution (default is the highest resolution)
             the interval you want the values to have (seconds per  value).   An
             optional  suffix  may  be  used (e.g. "5m" instead of 300 seconds).
             rrdfetch will try to match your request, but it  will  return  data
             even if no absolute match is possible. See "RESOLUTION INTERVAL".

     --start|-s start (default end-1day)
             start   of   the  time  series.  A  time  in  seconds  since  epoch
             (1970-01-01) is required. Negative numbers are relative to the cur‐
             rent time. By default, one day worth of data will be  fetched.  See
             also  "AT-STYLE  TIME  SPECIFICATION" for a detailed explanation on
             ways to specify the start time.

     --end|-e end (default now)
             the end of the  time  series  in  seconds  since  epoch.  See  also
             "AT-STYLE  TIME SPECIFICATION" for a detailed explanation of how to
             specify the end time.

     --align-start|-a
             Automatically adjust the start time down to  be  aligned  with  the
             resolution.   The  end-time  is  adjusted by the same amount.  This
             avoids the need for external calculations described  in  RESOLUTION
             INTERVAL,  though if a specific RRA is desired this will not ensure
             the start and end fall within its bounds.

     --daemon|-d address
             Address of the rrdcached daemon. If specified, a "flush" command is
             sent to the server before reading the RRD files. This  allows  rrd‐
             tool to return fresh data even if the daemon is configured to cache
             values for a long time.  For a list of accepted formats, see the -l
             option in the rrdcached manual.

              rrdtool fetch --daemon unix:/var/run/rrdcached.sock /var/lib/rrd/foo.rrd AVERAGE

             Please  note  that due to thread-safety reasons, the time specified
             with -s and -e cannot use the complex forms described in  "AT-STYLE
             TIME  SPECIFICATION". The only accepted arguments are "simple inte‐
             gers". Positive values are interpreted as seconds since epoch, neg‐
             ative values (and zero) are interpreted  as  relative  to  now.  So
             "1272535035"  refers  to  "09:57:15  (UTC),  April  29th  2010" and
             "-3600" means "one hour ago".

   RESOLUTION INTERVAL
     In order to get RRDtool to fetch anything other than the finest  resolution
     RRA  both  the  start and end time must be specified on boundaries that are
     multiples of the desired resolution. Consider the following example:

      rrdtool create subdata.rrd -s 10 \
       DS:ds0:GAUGE:5m:0:U \
       RRA:AVERAGE:0.5:5m:300h \
       RRA:AVERAGE:0.5:15m:300h \
       RRA:AVERAGE:0.5:1h:50d \
       RRA:MAX:0.5:1h:50d \
       RRA:AVERAGE:0.5:1d:600d \
       RRA:MAX:0.5:1d:600d

     This RRD collects data every 10 seconds and stores its averages over 5 min‐
     utes, 15 minutes, 1 hour, and 1 day, as well as the maxima for 1 hour and 1
     day.

     Consider now that you want to fetch the 15 minute average data for the last
     hour.  You might try

      rrdtool fetch subdata.rrd AVERAGE -r 15m -s -1h

     However, this will almost always result in a time series that is NOT in the
     15 minute RRA. Therefore, the highest resolution RRA, i.e. 5  minute  aver‐
     ages, will be chosen which in this case is not what you want.

     Hence, make sure that

     1. both start and end time are a multiple of 900 ("15m")

     2. both start and end time are within the desired RRA

     So, if time now is called "t", do

      end time == int(t/900)*900,
      start time == end time - 1hour,
      resolution == 900.

     Using the bash shell, this could look be:

      TIME=$(date +%s)
      RRDRES=900
      rrdtool fetch subdata.rrd AVERAGE -r $RRDRES \
         -e $(($TIME/$RRDRES*$RRDRES)) -s e-1h

     Or in Perl:

      perl -e '$ctime = time; $rrdres = 900; \
               system "rrdtool fetch subdata.rrd AVERAGE \
                       -r $rrdres -e @{[int($ctime/$rrdres)*$rrdres]} -s e-1h"'

     Or using the --align-start flag:

      rrdtool fetch subdata.rrd AVERAGE -a -r 15m -s -1h

   AT-STYLE TIME SPECIFICATION
     Apart  from  the  traditional Seconds since epoch, RRDtool does also under‐
     stand at-style time specification. The specification is  called  "at-style"
     after  the  Unix  command at(1) that has moderately complex ways to specify
     time to run your job at a certain date and time. The at-style specification
     consists of two parts: the TIME REFERENCE specification and the TIME OFFSET
     specification.

   TIME REFERENCE SPECIFICATION
     The time reference specification is used, well, to  establish  a  reference
     moment in time (to which the time offset is then applied to). When present,
     it  should  come  first, when omitted, it defaults to now. On its own part,
     time reference consists of  a  time-of-day  reference  (which  should  come
     first, if present) and a day reference.

     The  time-of-day can be specified as HH:MM, HH.MM, or just HH. You can suf‐
     fix it with am or pm or use 24-hours clock. Some special times of  day  are
     understood  as  well,  including midnight (00:00), noon (12:00) and British
     teatime (16:00).

     The day can be specified as month-name day-of-the-month and optional  a  2-
     or  4-digit  year  number  (e.g.  March 8 1999). Alternatively, you can use
     day-of-week-name (e.g. Monday), or one of the words: yesterday, today,  to‐
     morrow.  You  can  also specify the day as a full date in several numerical
     formats, including MM/DD/[YY]YY, DD.MM.[YY]YY, or YYYYMMDD.

     NOTE1: this is different from the original at(1)  behavior,  where  a  sin‐
     gle-number date is interpreted as MMDD[YY]YY.

     NOTE2:  if  you specify the day in this way, the time-of-day is REQUIRED as
     well.

     Finally, you can use the words now, start, end or epoch as your time refer‐
     ence. Now refers to the current moment (and is also the default time refer‐
     ence). Start (end) can be used to specify a  time  relative  to  the  start
     (end)  time  for those tools that use these categories (rrdfetch, rrdgraph)
     and epoch indicates the *IX epoch (*IX timestamp 0  =  1970-01-01  00:00:00
     UTC).  epoch  is  useful to disambiguate between a timestamp value and some
     forms of abbreviated date/time specifications, because it allows one to use
     time offset specifications using units, eg.  epoch+19711205s  unambiguously
     denotes timestamp 19711205 and not 1971-12-05 00:00:00 UTC.

     Month  and day of the week names can be used in their naturally abbreviated
     form (e.g., Dec for December, Sun for Sunday, etc.). The words now,  start,
     end can be abbreviated as n, s, e.

   TIME OFFSET SPECIFICATION
     The  time  offset specification is used to add/subtract certain time inter‐
     vals to/from the time reference moment. It consists of a sign (+ or -)  and
     an  amount.  The  following  time  units can be used to specify the amount:
     years, months, weeks, days, hours, minutes, or seconds. These units can  be
     used  in  singular or plural form, and abbreviated naturally or to a single
     letter (e.g. +3days, -1wk, -3y). Several time units can be combined  (e.g.,
     -5mon1w2d)  or  concatenated  (e.g.,  -5h45min  =  -5h-45min  = -6h+15min =
     -7h+1h30m-15min, etc.)

     NOTE3: If you specify time offset in days, weeks,  months,  or  years,  you
     will  end  with the time offset that may vary depending on your time refer‐
     ence, because all those time units have no single well defined time  inter‐
     val value (1 year contains either 365 or 366 days, 1 month is 28 to 31 days
     long,  and  even  1 day  may  be  not  equal to 24 hours twice a year, when
     DST-related clock adjustments take place).  To cope with this, when you use
     days, weeks, months, or years as your time offset units your time reference
     date is adjusted accordingly without too much further effort to ensure any‐
     thing about it (in the hope that mktime(3) will take care of  this  later).
     This  may  lead  to  some  surprising  (or  even  invalid!)  results,  e.g.
     'May 31 -1month' = 'Apr 31' (meaningless) = 'May 1' (after  mktime(3)  nor‐
     malization); in the EET timezone '3:30am Mar 29 1999 -1 day' yields '3:30am
     Mar 28 1999' (Sunday) which is an invalid time/date combination (because of
     3am -> 4am DST forward clock adjustment, see the below example).

     In  contrast,  hours, minutes, and seconds are well defined time intervals,
     and these are guaranteed to always produce time offsets exactly  as  speci‐
     fied    (e.g.    for    EET    timezone,    '8:00 Mar 27 1999 +2 days'    =
     '8:00 Mar 29 1999', but since there is 1-hour DST forward clock  adjustment
     that  occurs  around  3:00 Mar 28 1999,  the  actual  time interval between
     8:00 Mar 27 1999 and 8:00 Mar 29 1999 equals 47 hours; on the  other  hand,
     '8:00 Mar 27 1999 +48 hours' = '9:00 Mar 29 1999', as expected)

     NOTE4:  The single-letter abbreviation for both months and minutes is m. To
     disambiguate them, the parser tries to read your mind :)  by  applying  the
     following two heuristics:

     1. If  m is used in context of (i.e. right after the) years, months, weeks,
        or days it is assumed to mean months, while in  the  context  of  hours,
        minutes,  and  seconds  it means minutes.  (e.g., in -1y6m or +3w1m m is
        interpreted as months, while in -3h20m or +5s2m m the parser decides for
        minutes).

     2. Out of context (i.e. right after the + or - sign) the meaning  of  m  is
        guessed from the number it directly follows.  Currently, if the number's
        absolute  value  is below 6 it is assumed that m means months, otherwise
        it is treated as minutes.  (e.g., -6m == -6m minutes, while  +5m  ==  +5
        months)

     Final NOTES: Time specification is case-insensitive.  Whitespace can be in‐
     serted freely or omitted altogether.  There are, however, cases when white‐
     space  is  required  (e.g., 'midnight Thu'). In this case you should either
     quote the whole phrase to prevent it from being taken apart by  your  shell
     or  use  '_'  (underscore)  or  ','  (comma) which also count as whitespace
     (e.g., midnight_Thu or midnight,Thu).

   TIME SPECIFICATION EXAMPLES
     Oct 12 -- October 12 this year

     -1month or -1m -- current time of day, only a month before (may yield  sur‐
     prises, see NOTE3 above).

     noon  yesterday  -3hours  --  yesterday  morning;  can also be specified as
     9am-1day.

     23:59 31.12.1999 -- 1 minute to the year 2000.

     12/31/99 11:59pm -- 1 minute to the year 2000 for imperialists.

     12am 01/01/01 -- start of the new millennium

     end-3weeks or e-3w -- 3 weeks before end time (may be used  as  start  time
     specification).

     start+6hours  or  s+6h -- 6 hours after start time (may be used as end time
     specification).

     931200300 -- 18:45 (UTC), July 5th, 1999 (yes, seconds since 1970 are valid
     as well).

     19970703 12:45 -- 12:45  July 3th, 1997 (my favorite, and it has  even  got
     an ISO number (8601)).

ENVIRONMENT VARIABLES
     The  following  environment variables may be used to change the behavior of
     "rrdtool fetch":

     RRDCACHED_ADDRESS
         If this environment variable is set it will have  the  same  effect  as
         specifying  the  "--daemon"  option  on  the  command line. If both are
         present, the command line argument takes precedence.

AUTHOR
     Tobias Oetiker <tobi@oetiker.ch>

1.11.0                             2026-08-08                        RRDFETCH(1)
